DNA连接酶的结构与功能

在ＤＮＡ合成中 ,合成方向为 5′→ 3′ ,即一条链上是连续复制的 ,而另一条链的复制是不连续的 ,必须先合成岗崎片段 (真核细胞的岗崎片段为 10 0ｂｐ ,原核细胞的为 10 0 0ｂｐ)。ＤＮＡ连接酶的作用就是催化岗崎片段的连接以完成ＤＮＡ的合成。另外 ,ＤＮＡ连接酶在ＤＮＡ修复过程中也起重要作用 ,如在切除修复中 ,切除损伤的ＤＮＡ片段 ,以未受损伤的链作为模板合成一条新的ＤＮＡ链后 ,ＤＮＡ连接酶将新合成的ＤＮＡ链与原来的ＤＮＡ链之间的缺口封闭完成ＤＮＡ的修复。ＤＮＡ链未封闭的缺口对细胞具有潜在的危险性 ,所以 ,ＤＮＡ连接…     

中心体复制及调控机制研究进展

中心体是动物细胞内最主要的微管组织中心。此外,它还参与纺锤体组装、纤毛发生和细胞迁移等一系列生物过程。中心体异常不仅与肿瘤的发生密切相关,并且还会导致一些发育方面的疾病。该文总结了中心体的结构、复制过程及其调控机制等方面的研究进展,并讨论了中心体异常与肿瘤发生及发育相关疾病的关系,为更深入了解产生中心体异常的原因及一些相关疾病的诊断和治疗提供参考。     

体细胞核移植与中心体遗传

体细胞克隆虽然在多种哺乳动物中成功获得后代, 但仍存在一系列的问题需要解决。克隆胚胎的发育能力由核移植后几小时内的细胞和分子过程决定, 包括染色体分离和纺锤体的重新组装。中心体的正常组成和分布能保证染色体分离的准确性及新生和出生后克隆动物发育过程中的基因组稳定性。文章在分析哺乳动物体细胞克隆存在的问题和简介中心体结构功能的基础上, 综述了中心体在配子和受精卵发育过程中的遗传机制, 同时阐述了体细胞克隆胚胎中心体及其相关蛋白的研究现状。     

甾体激素的作用机制及其受体的结构和功能

本文介绍了甾体激素作用机制的研究进展,以及受体参与作用的模式。甾体激素受体的核内定位,是一个重要的突破。对于受体Domain结构的研究及其与靶基因HRE相互作用,则是近年来更深入的发展。另一方面,细胞内专一性染色质组份接受了受体携带的大部分激素信息,也成为研究甾体激素调控机制的一个不可忽视的方面。     

厌氧氨氧化体的组成、结构与功能

厌氧氨氧化(Anammox)是微生物和环境领域的研究热点之一。厌氧氨氧化菌(AnAOB)是Anammox的功能载体。不同于大部分原核微生物,AnAOB具有独特的细胞器——厌氧氨氧化体,它是进行Anammox代谢的场所。研究厌氧氨氧化体有助于探明厌氧氨氧化菌的代谢特性。本文综述了厌氧氨氧化体的组成、结构与功能,以期为从事Anammox研究的同行提供参考。     

细胞骨架与中心体的分离过程

中心体作为细胞微管组织中心,对于细胞的生理活动具有重要的调控作用.在G2期末和有丝分裂期开始阶段,复制之后的中心体需要向细胞核两端运动,到达形成双极纺锤体的位置.这一过程受到微管和微丝两个骨架系统的调控.在相关动力蛋白的驱动下,两种骨架相互配合,共同完成中心体的分离过程,从而保证细胞顺利进入有丝分裂期.本文分析和比较了两种骨架蛋门对下中心体分离过程中所发挥的作用.     

BKCa通道的结构与功能

BKCa通道将细胞膜电特性与细胞信号系统联系在一起,在细胞功能实现中起着重要作用。该通道广泛且又较高密度地表达于许多物种的多种组织,其分子结构复杂,丰富的超家族成员具有各自不同的表达分布。BKCa通道的分子结构由α亚单位和β亚单位构成,其中α亚单位形成通道的孔道区和活性调节区域,β亚单位修饰通道活性的调节特性。BKCa通道开放几率大、电导率高、调控位点多,并且不同的超家族成员表现出不同的功能特征,如细胞膜电位感受性、细胞内游离钙离子敏感性等。文章概述BKCa通道的分子结构和功能特征。     

GPCR二聚体结构及功能

G蛋白偶联受体（G-protein coupled receptor,GPCR）是最广泛表达的膜蛋白家族之一,其可接收胞外信号刺激,通过自身构象变化激活胞内G蛋白等一系列信号通路,参与众多生理调节过程,具有重要的功能,因此其也是重要的药物靶点。GPCR二聚化是调控其功能的重要形式之一,靶向GPCR二聚体开发药物是药物研发的一个新方向。越来越多的研究报道了GPCR二聚化及其结构与功能调控的机制,本文综述了GPCR二聚体结构及功能的研究进展,为了解GPCR二聚体的发现、二聚化方式、功能调控机制,及进一步靶向GPCR二聚体药物开发提供了研究基础。     

真核细胞DNA聚合酶δ的结构与功能

DNA聚合酶δ(Polδ)在真核细胞的DNA复制过程中具有核心酶的作用,同时还参与DNA的修复。Polδ是一种由多个亚基组成的复合体,目前已从哺乳动物、裂殖酵母和芽殖酵母等多种真核生物细胞中分离出,并对它们的亚基组成进行了分析,但还未得到确切一致的结果。Polδ在DNA复制中的具体作用已基本了解,它参与催化整个前导链的复制以及一些或大部分滞后链的复制。此外,Polδ还参与DNA的修复,此酶的这一功能可减少DNA的变异,但目前对其作用机理还知之较少。在Polδ活性调控方面,主要研究了一些相关蛋白因子对Polδ活性的调控作用以及转录因子对催化亚基表达的调控作用。     

IL－6受体结构与功能的研究进展

IL-6是一个多功能的细胞因子,其生物学作用在很大程度上受IL-6受体(IL-6R)结构和功能的影响.IL-6R由两条多肽链组成,即配体结合链gp80和信号传导链gp130.它们在结构和功能上既有分工又有合作.两种亚基组成的高亲和力IL-6R是介导细胞效应所必需的.IL-6Rα中的造血功能区属于造血因子受体超家族成员,它决定着结合IL-6的能力.然而gp130则是多种细胞因子共用的信号传递分子,其胞内段含有与酪氨酸激酶活化有关的保守成分.IL-6+IL-6R复合物通过诱导gp130的聚合来活化胞内的多种激酶分子和转录因子并最终导致有关基因的表达.     

Re-evaluating centrosome function

Over the past 100 years, the centrosome has risen in status from an enigmatic organelle, located at the focus of microtubules, to a key player in cell-cycle progression and cellular control. A growing body of evidence indicates that centrosomes might not be essential for spindle assembly, whereas recent data indicate that they might be important for initiating S phase and completing cytokinesis. Molecules that regulate centrosome duplication have been identified, and the expanding list of intriguing centrosome-anchored activities, the functions of which have yet to be determined, promises continued discovery.     

Identification and function of the centrosome centromatrix

Centrosomes direct the organization of microtubules in animal cells. However, in the absence of centrosomes, cytoplasm has the potential to organize microtubules and assemble complex structures such as anastral spindles. During cell replication or following fertilization, centrioles that are incapable of organizing microtubules into astral arrays are introduced into this complex cytoplasmic environment. These centrioles become associated with pericentriolar material responsible for centrosome-dependent microtubule nucleation, and thus the centrosome matures to ultimately become a dominant microtubule organizing center that serves as a central organizer of cell cytoplasm. We describe the identification of a novel structure within the pericentriolar material of centrosomes called the centromatrix. The centromatrix is a salt-insoluble filamentous scaffold to which subunit structures that are necessary for microtubule nucleation and abundant in the cytoplasm bind. We propose that the centromatrix serves to concentrate and focus these subunits to form the microtubule organizing center. Since binding of these subunits to the centromatrix does not require nucleotides, we propose a model for centrosome assembly which predicts that the assembly of the centromatrix is a rate-limiting step in centrosome assembly and maturation.     

Interphase centrosome organization by the PLP-Cnn scaffold is required for centrosome function

Pericentriolar material (PCM) mediates the microtubule (MT) nucleation and anchoring activity of centrosomes. A scaffold organized by Centrosomin (Cnn) serves to ensure proper PCM architecture and functional changes in centrosome activity with each cell cycle. Here, we investigate the mechanisms that spatially restrict and temporally coordinate centrosome scaffold formation. Focusing on the mitotic-to-interphase transition in Drosophila melanogaster embryos, we show that the elaboration of the interphase Cnn scaffold defines a major structural rearrangement of the centrosome. We identify an unprecedented role for Pericentrin-like protein (PLP), which localizes to the tips of extended Cnn flares, to maintain robust interphase centrosome activity and promote the formation of interphase MT asters required for normal nuclear spacing, centrosome segregation, and compartmentalization of the syncytial embryo. Our data reveal that Cnn and PLP directly interact at two defined sites to coordinate the cell cycle–dependent rearrangement and scaffolding activity of the centrosome to permit normal centrosome organization, cell division, and embryonic viability.     

新型海洋防污剂应用组分的简述

海洋防污涂料是通过海洋防污剂的可控释放,与海洋污损生物发生作用,从而阻止海生物在物体表面附着。海洋防污涂料中最重要的组成部分是基体树脂和海洋防污剂。海洋防污剂主要是从农药、杀虫剂、杀菌剂、防霉剂以及带有生物活性的聚合物中筛选出来的,随着海洋环境保护日益严格,制备和筛选高效、广谱的海洋防污剂对海洋防污涂料的发展日显重要,本文对现有的防污剂材料作了简述。     

Thermotolerant cells possess an enhanced capacity to repair heat-induced alterations to centrosome structure and function

To study the mechanism of thermotolerance, the adaptive response by which cells become transiently resistant to killing by heat shock, we have focused on the centrosome, an organelle whose disorganization is closely correlated with thermal killing in Chinese hamster ovary (CHO) cells. Centrosome structure was studied by use of antisera directed against pericentrin, a 220 Kd protein of the pericentriolar material (PCM). Centrosome function was measured in intact cells by performing microtubule regrowth following exposure to the drug nocodazole. Immediately following heating at 45°C for 4–18 min, centrosomal staining by antipericentrin decreased. Thereafter, staining gradually recovered, although abnormal configurations of staining appeared in heated cultures 10–20 h later. In contrast, abnormal patterns of staining rarely developed in thermotolerant cultures. Centriole number was not perturbed by heat, indicating that the heat effect was specific for the PCM. Heat also caused an immediate reduction in the number of microtubules nucleated by the PCM. As for staining by antipericentrin, microtubule nucleation recovered during 3–20 h at 37°C after heating. The immediate, heat-induced decrease in antipericentrin staining or microtubule nucleation was similar in thermotolerant and nontolerant cells. In contrast, the inhibition for both endpoints recovered to control levels much more quickly in thermotolerant cells than in nontolerant cells. Furthermore, new protein synthesis was not required for the recovery of microtubule nucleation. These data show that thermotolerant cells have an enhanced capacity to repair thermal damage to centrosome structure and function, and suggest that a faster rate of recovery prevents disorganization of the PCM that is observed in nontolerant cells several hours after heating. © 1995 Wiley-Liss, Inc.     

巨胞饮的机制及功能的研究进展

巨胞饮（macropinocytosis）是内吞的一种形式,指在某些因素刺激下,细胞膜皱褶形成大且不规则的原始内吞小泡,它们被称为巨胞饮体。巨胞饮体的直径一般为0．5～2μm,有时可达5μm。与其它内吞形式的小泡相比,巨胞饮体直径较大,为非选择性地内吞细胞外营养物质和液相大分子提供了一条有效途径。最近的研究表明,巨胞饮具有清除凋亡细胞、参与免疫反应、介导某些病原菌侵袭细胞、更新细胞膜等功能。